The present invention relates to a data processing system having an apparatus for controlling interruptions in the program, wherein a series of input-output units I/O is connected by way of a system bus to a central unit which is capable of accepting at least one category of vectored interrupts requested by the I/O units and a category of non-vectored interrupts generated by the operating system of the program in consequence of predetermined operations.
In a data processing system of the above-indicated type, vectored interrupts are capable of masking non-vectored interrupts which therefore are of lower priority than the vectored interrupts. However, such a system is unable to resolve the conflicts which derive from simultaneous requests for a plurality of interrupts of the same category.
Other systems are known in which each I/O unit is assigned a predetermined priority which is defined by a particular code despatched to the central unit. When there is a large number of interrupting units, such codes require a relatively high level of circuitry resources which complicate operation of the central unit.